Prestressed membrane structure

ABSTRACT

A building structure has a plurality of elongated flexible compression arches or ribs to which a flexible membrane is operatively connected to span spaces between the arches in a folded pattern with the arches located at the apices of the folds and valleys formed between the apices. A plurality of cables are operatively associated with the membranes by prestressing and are located in the valleys formed between the arches in order to maintain the membrane in tension under substantially all load conditions so that the flexible arches are braced against buckling by the membrane. As a result, the flexible components of the structure cooperate to form a relatively rigid structural system capable of spanning relatively long distances for covering sports stadiums and the like.

United States Patent [1 1 Geiger et al.

[ PRESTRESSED MEMBRANE STRUCTURE [76] Inventors: David H. Geiger, 788Riverside Dr.,

New York, NY. 10032; Horst Berger, 18 Chestnut Dr., Hastings on Hudson,NY. 10706 [22] Filed: Oct. 26, 1973 [21] Appl. No.: 409,779

Related US. Application Data [62] Division of Ser. No. 234,238, March13, 1972, Pat.

[52] US. Cl 135/1 R; 52/23; 52/80; 52/82 [51] Int. Cl. E04b 1/347; A43f1/00 [58] Field of Search 135/1 R, 3 R, 5 R; 52/222, 52/86; 1/18, 80, 82

1 References Cited UNITED STATES PATENTS 2,021,480 11/1935 Davidson108/23 2,516,369 9/1950 Harris.. 135/1 2,881,718 4/1959 Stromeyer..108/1 2,988,096 6/1913 Otto 13511 3,134,200 5/1964 MOSS 50/534 3,198,2008/1965 Sanders... 135/1 3,465,764 9/1969 Huddle 135/1 3,473,272 l0/l969Hasselquist 52/63 June 3, 1975 3,474,802 10/1969 Loring 135/1 FOREIGNPATENTS OR APPLICATIONS 1,024,748 1966 United Kingdom 1,132,316 1958Germany... 135/1 R 1,345,881 1963 France 52/86 Primary Examiner-John E.Murtagh Attorney, Agent, or Firm-Arthur V. Smith, Esq.; Pasquale A.Razzano, Esq.

[57] ABSTRACT ble arches are braced against buckling by the membrane. Asa result, the flexible components of the structure cooperate to form arelatively rigid structural system capable of spanning relatively longdistances for covering sports stadiums and the like.

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PRESTRESSED MEMBRANE STRUCTURE This is a division, of application Ser.No. 234,238, filed Mar. 13, 1972, now US. Pat. No. 3,807,421.

The present invention relates to building structures and moreparticularly to a structural system suitable for use as temporary orpermanent enclosures of various sizes.

In recent years there has been an increased demand for inexpensivehousing and shelter structures due to the increased costs of labor andmaterial required for erecting previously proposed types of buildings.Moreover, this demand includes a need for flexible building structureswhich can be readily converted from temporary to permanent usage andwhich are readily assembled and maintained. Similarly, lightweight andeasily erected structures are required for spanning relatively largedistances or spaces to form domes for stadiums and like structures.

In previously proposed building structures of both a temporary andpermanent type, some or all of the structural components utilized arerigid members in order to provide the structure with stability. Suchmembers normally account for a substantial portion of the cost of thebuilding structure and are relatively difficult to transport from thefabrication plant to the building site. As a result, temporary shelters,particularly emergency shelters for use in hurricane or earthquakedisasters or the like are both relatively expensive and difficult totransport to the required location. Moreover, once at the site, suchstructures are relatively difficult to erect, normally requiringspecialized equipment or tools and large numbers of. laborers.

Accordingly, it is an object of the present invention to provide arelatively simply constructed and erected structure which is economicalin manufacture and use.

Yet another object of the present invention is to provide a buildingstructure which is readily erected and converted from emergency ortemporary shelter to a permanent use.

Yet another object of the present invention is to provide a buildingstructure or system which is suitable to a number of uses including thatof forming entire building structures or portions of structures, such asdomes for stadiums and the like.

In accordance with an aspect of the present invention, a buildingstructure is provided in which a plurality of compression arches, whichare formed from normally flat flexible structural members, are held inan arched configuration to support a flexible membrane. The latter isoperatively connected to the arches in a folded configuration having aplurality of ridges and valleys, with the flexible arches located at theridges in the folded membrane and the valleys therein taking shapebetween the ridges. A flexible cable is located between the arches inthe membrane valley therebetween, and is prestressed to hold themembrane in tension against the arches. As a result, the flexible archesare braced against buckling by the tensioned membrane, undersubstantially all load conditions, so that a relatively rigid structureis created from the combination of the flexible arches, flexiblemembrane and flexible cables.

As will be described more fully hereinafter, the structure of theinvention is relatively simple to erect because of the lightweight andflexible nature of the various components utilized therefor.Accordingly, the structure is readily erected at an emergency site, for

use as temporary emergency shelter. Moreover, the components utilized toform the structure are lightweight, economic and readily transportableso that the structure is extremely economical for use in emergencysituations. Since the structure can be readily transported andassembled, it is quite suitable for home use, as for example, a hometemmis court shelter or the like.

The basic principal of the invention is the cooperation of the flexiblearches, which serve as compression members in the structure, and thetensioned membrane and stressed cables which tension the membrane tobrace the arches and form the rigid structure. The rigidity of the finalstructure is produced by means of stressing of the tensile cables in thevalleys formed in the membrane. By putting these members under tension,a tensile stress is produced in the membrane, which in turn produces aload on the compression member or flexible arch, thus putting all of thecomponents of the structure under a prestressed condition. All of thecomponents are interconnected with each other in any convenient fashion,so that they form a three-dimensional space frame structure of which nopart can move without movement of all of the other parts. With the basicarrangement and relation of the components, as described and claimedherein, the structure can be designed to a shape and stress so thatunder any design load case, the components will not lose this contactwith each other so that the tensile members, i.e. the cable and membranewill always remain in tension, while the compression members will alwaysremain in compression. As a result, the shape of the structure can becontrolled to a degree such that the compression members cannot buckleand no member in the system can become overstressed.

This principal of cooperating elements provides an extremely flexiblebuilding system which can be used to form building structures or domeshaving a variety of shapes and patterns and which can be arranged withrespect to one another in various arrays to achieve complete flexibilityin the design layout and construction. Moreover, the patterns andarrangement of the arches and cables in the structure are repetitive sothat standardized materials and sizes can be utilized throughout thebuilding, which materials are readily presently available. This, ofcourse, greatly reduces the cost of the structure and renders itsubstantially more economical than previously proposed structures.

The above, and other objects, features and advantages of this invention,will be apparent in the following detailed description of anillustrative embodiment thereof which is to be read in connection withthe accompanying drawings, wherein:

FIG. 1 is an elevational view with parts broken away of a buildingstructure constructed in accordance with one embodiment of the presentinvention;

FIG. 2 is a plan view, with parts broken away, of the building structureillustrated in FIG. 1;

FIG. 3 is a sectional view taken along line 33 of FIG. 1;

FIGS. 4 and 5 are diagrammatic illustrations of the operation of thepresent invention;

FIG. 6 is a plan view, similar to FIG. 3, of another embodiment of thepresent invention;

FIG. 7 is an elevational view of the building structure illustrated inFIG. 6; I

FIG. 8 is a plan view of a building structure constructed in accordancewith another embodiment of the invention;

FIG. 9 is an elevational view of the building structure illustrated inFIG. 8;

FIG. 10 is a sectional view taken along line 10-10 of FIG. 8; and

FIGS. 11 and 12 are diagrammatic illustrations of relative arrangementsof a plurality of building structures constructed in accordance with theembodiment of FIG. 8.

Referring now to the drawing in detail, and initially to FIGS. 1 and 2thereof, it is seen that a building structure 10, embodying the presentinvention, is formed from a plurality of flexible arches or ribs 12which extend generally parallel to each other to form a generallyrectangular building structure when viewed in plan. Arches 12 arecovered by and operatively connected to a flexible membrane 14 which ispositioned on the arches in a *folded" configuration so that themembrane has a plurality of ridges 16 and valleys 18 therebetween. Theridges 16 formed in the folded membrane are located along arches 12while the valleys 18 therein are located between the arches.

Arches 12 are normally flat members formed of a flexible material, suchas thin elongated bars of aluminum, wood or the like, which arerelatively light in weight and readily transportable. These arches areinitially placed in parallel relation to each other and are then bowedinto their arched configuration to support membrane 14 in the completedstructure, as more fully described hereinafter.

Before arches 12 are bowed, the flexible membrane 14 is placed thereon.Membrane 14 is preferably formed of a woven synthetic fabric material,although it is contemplated that other materials such as canvas or thinmetallic foil membrane may also be utilized. In any case, the membraneis mechanically connected to the arches, as for example, by sewing, orthe like, although it is also contemplated that the system of thepresent invention will operate efficiently if the membrane is merelyplaced on top of the arches, with no direct mechanical connectiontherebetween except at the edges of the membrane. In the lattersituation, the frictional engagement between the arches and the membraneand the end attachment of the membrane to the arches will be sufficientto achieve the desired structural stability and rigidity in thebuilding.

Arches 12 are braced against lateral movement and buckling by membrane14 which is held constantly under tension in all load conditions bycables 20 located in membrane valleys 18.. Cables 20 in turn areprestressed by edge cables 22 located at opposite sides of the arches.These are secured at their ends 24 to the ends 25 of the outermostarches 12 in the building and pass over guide pulleys or rollers 26rotatably mounted at the ends of intermediate arches 12. The ends ofarches 12 are pivotally mounted in base support or connectors 28 whichcan be simply seated on the ground or secured to footings to make thestructure permanent. Between arches l2, cables 22 are guided overpulleys 30 mounted on the ends 32 of cables 20 and thus cables 22 areoperatively connected to cables 20 to prestress them. Cables 22 are thustriangulated, that is, as seen in FIG. 1, they form triangularl shapedarrays between arches 12, with their points of connection to cables 20being located at the apex of the triangles.

In this manner, cables 20 and 22 are prestressed, with cables 22 servingto equilibrate the thrust of the arches 12 at the supporting structures28, to draw cables 20 tightly against membrane 14 so that the membraneis held in tension. It is noted that the terms prestress or prestressingas used herein have their conventional meaning in the construction arts,that is, that a predetermined stress or pattern of stress is applied tothe structure prior to adding superimposed loads thereon.

With the relative configuration of the components thus described, theamount of prestressing can be adjusted so that membrane 14 will beconstantly under tension in all load conditions. As a result, arches 12,which act to take the compression loads on the structure, are bracedagainst buckling and the entire structure is thus substantially rigid.

The ends of building 10, as illustrated in FIGS. 1 and 2, are formedfrom a pair of additional flexible arches 34 which are also pivotallyconnected to the end base support members 28. The areas 36 between thetriangulated cables 22 can be left open to permit access to the buildingstructure or, alternatively, the membrane 14 may extend down into theareas 36 to close the sides of the building. The membrane structure inthis area would also be tensioned by cables 20 and 22 so that themembrane at those points is substantially rigid. In addition, it isnoted that the free edges 37 of membrane 14 are secured tightly to theground adjacent the building by conventional earch anchors or stakes 39in order to maintain the prestressing or tension in the membrane at thevertical ends 39 thereof and in the areas 36 between cables 22 and theground.

In erecting the structure illustrated in FIG. 1, the normally flatflexible arches 12 are drawn into their bowed or arched configuration,by means of a cable 38 extending between the base support members 28 towhich the arches are pivotally connected in any convenient manner.Referring to FIG. 3, each cable 38 is rigidly connected at one end toone of the base support members 28 associated with their respective archby a conventional cable anchor system 40. The other end of cable 38 ispassed through a similar anchor 42 at the opposite base support member28 (at the left in FIG. 3) and is drawn therethrough. As a result, theright end 44 of each arch l2 (and the base member 28 to which it isconnected) is moved in to the left, as seen in FIG. 3, and the arch isbowed, thereby lifting membrane 14 into its folded configuration. Whenthe desired bow or arch is obtained, cable 38 is locked in position inanchor 42 so that the arch configuration is maintained. It is noted thatduring use of the structure, cables 38 serve to equilibrate superimposedloads, such as snow loads, imposed on the arch during use of thestructure. Alternatively, cables 38 may be eliminated and cables 20 and22 may then be used alone to maintain bow in the arches and equilibratesuperimposed loads.

Thus, it is seen that the structure is designed so that the cables 20,22 serve to equilibrate the natural thrust of the flexible arches 12 andto tension membrane 14, while cables 38 serve to equilibrate the thrustloads created by superimposed dead loads on the structure. As a result,a rigid structure is formed from only flexible components and thisstructure will maintain its rigidity under substantially all loadconditions.

Referring to FIGS. 4 and 5 of the drawing, the basic operation of thebuilding structure during use is schematically illustrated. As seen inFIG. 4, compression arches 12 have membrane 14 superimposed thereon,with a prestressed cable located in the valley 18 between the arches andmaintaining the membrane in tension. In the event a superimposed load isapplied to the building structure, such as for example, a snow load, asrepresented by the arrows S in the drawing, arches 12 would tend to movedownwardly under the load. Such downward movement would cause the valleyof the membrane to move upwardly in the direction of the arrow T torelieve the stress on the membrane. However, prestressed cable 20prevents this upward movement of the membrane at point T, therebymaintaining the tension in membrane 14, and as a result, the membranecontinues to brace arches 12 against buckling. Thus, the superimposedload S is transmitted through the arches in compression to the basesupport members 28 where it is equilibrated by cables 22 and thehorizontal cables 38.

It is noted that cables 38, in the embodiment illustrated in thedrawings, are located on the ground, and such cables would be covered bya false flooring arrangement in the building to prevent interferencewith the use thereof. Alternatively, the entire structure illustrated inFIGS. 1-3 could be utilized as a dome for a building such as a stadiumor the like, with base support members 28 seated on a peripheral wall orindividual columns, so that the structure shown would be raised abovethe ground. In that event, cables 38 would be above the ceiling of thestructure and out of the way of interference with the use thereof.

Referring to FIG. 5 of the drawing, a somewhat modified embodiment ofthe invention is illustrated, where in lieu of the single cable 20,three cables 20' are utilized. Each of these cables serves the samefunction as cable 20 in that they are prestressed and serve to maintainthe tension in membrane 14 between arches 12. In addition, more than onearch may be used at the ridges of the membrane, depending upon thedesign of the structure, size of the load to be carried, and the size ofthe building.

Another embodiment of the present invention is illustrated in FIGS. 6and 7 of the drawings. This embodiment is similar to the embodiments ofFIGS. 13 in that it is generally rectangular in plan. However, in thiscase, arches 12 are arranged in pairs forming a plurality of Xs acrossthe longitudinal axis of the building. As a result, the ridges 16 formedin membrane 14 are skewed with respect to the longitudinal axis of thebuilding and a greater number of valleys are formed therebetween. Thatis, valleys 46 are formed between the ends of arches 12 and additionalvalleys 48 are formed between the legs of each of the Xs. In each ofthese valleys cables 20 are placed in order to pretension the fabric ina manner similar to that described in the previous embodiment.

With the arches arranged in this manner, the loads imposed upon thestructure are triangulated and distributed to improve the equilibriumand stability of the building structure. In this regard, as illustratedin FIG. 7, the ends of each arch 12 are connected at a common point 50with the end of an arch from an adjacent pair of arches. At these commonpoints the arches are rigidly secured to rigid structures 52 which serveto support the arch members above the ground and are interconnected bytying cables corresponding to cables 38 of the prior embodiment, whichmaintain the arches in a bowed configuration and equilibrate the thrustthereof. Support structures 52 are rigid inverted V- shaped arrangementswhich serve to triangulate the forces applied to the dome and transmitthem to the ground at footings 54. Moreover, cables 20 are anchored inany convenient manner to the support structures 52 on the opposite sidesof the structure to hold membrane 14 under tension in cooperation withthe action of arches 12.

The ends of the structure illustrated in FIG. 7 are formed by flexiblearches 56 which are secured to the membrane 14 and the supportstructures 52 at the ends of the building. Additional membrane sectionsmay be used to close the ends of the arches or these ends may be leftopen for a temporary shelter. As with the prior embodiment, earthanchors or stokes 39 are used to secure the free edge of the membrane tothe ground to maintain the vertically extending ends 34' of the membranein tension. Alternatively, prefabricated end wall segments having doorsand windows therein can be utilized to make this structure asemi-permanent dwelling or emergency housing structure.

Referring now to FIGS. 8 through 10, yet another embodiment of theinvention, which utilizes the basic principles of operation andconstruction of the previously described embodiments, is disclosedwherein a dome shaped structure 60 is provided, having a regularpolygonal configuration in plan. In this embodiment flexible arches arealso utilized, however, the arches are formed in two sections 12a and12b. These sections are normally flat members and are interconnected inradial alignment with each other by a rigid annular central ring 64. Asillustrated in FIGS. 8 and 10, this interconnection may be a simple malefemale arrangement, in which the ends 66 of the arches are received inradial apertures 68 in the ring. Such an arrangement is suitable for usein temporary structures. For more permanent structures, the connection Ccan be made rigid by bolting, welding or the like. All of the arches 12are connected in this manner to central ring 64 and the flexiblemembrane 14 is placed over the arches. As in the prior embodiments, themembrane may be mechanically secured to the arches by sewing or the likeor it may simply be laid across the arches for frictional engagementtherewith.

After membrane 14 is placed over arches 12, central ring 64 is raised sothat the arches bow of their onw flexibilith from the central ring tothe ends, thereby forming the ridges 16 and valleys 18 in the membrane.The free ends 70 of each of the arches are rigidly secured to a pair ofangularly related rigid columns 72 forming an inverted V-shapedsupporting structure which hold the arches in their bowed configurationand thus maintains the arches in Compression. Columns 72 are in turnconnected, as illustrated in FIG. 9, to a support ring or foundationanchor 74 which defines the outer peripheral shape of the structure.

With the components positioned membrane this arrangement, radiallyextending cables 76, which are secured at their inner ends 78 to ring64, are positioned over membrane 14 in the valley 18 formed betweenridges 16 of the membrane. These cables are secured at their outer ends80 to foundation anchors 74 and are prestressed, in order to tensionmemberane 14. A peripheral cable 82 is engaged with the free ends 70 ofarches 12 in a groove formed in the end of the arch, or over a pulleyrotatably mounted in the arch, and prestressed in a conventional manner,for example, by a turn buckle secured to its ends in order toequilibrate superimposed loads on the dome structure.

In this embodiment of the invention the free edge 34 of the membrane issecured to edge cables 86 which are tensioned about the invertedV-shaped supports provided by columns 72. Each cable 86 is a separatemember secured at its ends 88 to footing anchors 74 and contacting theapex 90 of each inverted V at its center. In this manner the stress inmembrane 14 is transferred to supports 74 only at their ends and thusthese supports are subjected only to compressive stresses. As a result,these columns can have a smaller diameter than would be necessary if themembrane were connected directly to them. This arrangement is alsosuitable for use with the previously described embodiments.

Accordingly, it is seen that the roof skin or membrane 14 of each of theabove described embodiments is utilized as a structural component of thebuilding, which, by the prestressing of cables 20, becomes an integralpart of the whole building structure. The membrane thus functions as anelement spanning between the arch ribs, to provide shelter for theenclosure, while it also acts as a tensile and shear structural webinterconnecting the cables and arches.

The peripheral cables of the dome structure illustrated in FIGS. 8 to 10serve to carry the thrust of the dome ribs and to produce sufficientstress in the membrane so that it remains taught under any loadcondition, thereby guaranteeing an integral composite structure made ofcompression ribs, tensile cables and the membrane surface. Each of thesecomponents is normally flexible, but with the arrangement of thecomponents as described in accordance with the present invention, renderthe structure relatively rigid.

The buckling stability normally required of an arch ridge for domestructures is usually supplied by constructing the rib as a rigidmember, making the ribs or arches relatively expensive and difficult totransport. By the present invention the stability is replaced by theintegral structural system described wherein the membrane restrains thearch from buckling. The degree of restraint required can be achieved byvarying the spans between the arches, the slope of the membrane againstthe arch, the stiffness of the cable selected, and the amount of stressthe cable and membrane produce.

The dome made in accordance with this invention permits a simpleerection procedure as described, in order to create an extremelylightweight roof structure which is translucent, depending upon thematerial se lected for the membrane 14, and waterproof. The structurecan be put up by very simple systems in a very short period of time andcan readily span large spaces. In fact, it is contemplated thatstructures such as illustrated in FIGS. 8 through 10 can easily span aspace from'5f to 1,000 feet in diameter and can be built at asubstantially lower cost than conventional structures.

The ribs or arches used in each of the above described embodiments canbe formed of many different types of materials, for example, laminatedwood or aluminum strips, or integral or solid thin aluminum or othermetal or wood materials. Preferably they are of lightweight constructionand readily transported. The compression members or arches should havesufficient flexibility so that initially they are straight members butcan be curved to the appropriate are without exceeding their elasticlimit, i.e. without forming a permanent deformation therein.

The cables utilized in all embodiments are preferably formed of highstrength steel, particularly for relatively large buildings, althoughfor temporary structures and structures of smaller size, other materialsmay be utilized. The membrane, on the other hand, is made of a materialwhich can be folded for the purpose of shipment and can be shaped to fitthe form of the structure as required.

As a result, it is seen that the structure requires no rigid orprecurved components, as has been heretofore required with buildingstructures. Rather, the structure is made entirely of straight flexibleelements of extremely light weight. The fabric can be folded into asmall package and the cables rolled into rings for transportation, whilethe flexible compression members come in flat easily manageable piecesso that the whole structure can be transported easily by any means oftransportation and erected with the help of very light equipment andvery few workmen.

In summary, the rigidity of the final structure is produced by means ofprestressing of the tensile cables 20 located in the valleys between themembrane ridges. By putting these cables under tension, a tensile stressis lTOdUCed in the membrane 14, which, in turn, produces a load on thecompression members or arches 12, thus putting all components understress and interconnecting them with each other into a threedimensionalspace structure of which no part can move without movement of all otherparts. The structure can be shaped and stressed so that under any loadcondition the components will not lose this contact with each other andthe tensile members will remain in tension, the compression members willremain in compression and the shape will be controlled to such a degreethat the compression members cannot buckle and that no member willbecome overstressed.

Such domes can be erected rapidly and inexpensively at an emergency siteto provide temporary shelter. However, because the structure isrelatively rigid, the structure can be conveniently converted into asemipermanent or permanent housing unit. This can be done by theprovision of modular interior components providing sanitary facilitiesand individual rooms, floors, and ceilings. In addition, because of theregular peripheral configuration of the dome structure, the domes can beplaced in a variety of arrays or patterns to provide a pleasing andfunctional appearance. Two of such systems are illustrated by way ofexample in FIGS. 11 and 12 wherein it is seen that the domes can beclustered to provide interior or exterior court yards and passagewayswhile providing a plurality of closely related building or housingunits.

It is also to be noted that each structure constructed in accordancewith the invention has a plurality of similar parts so that eachcomponent therein may appear a fairly large number of times. As aresult, even a fairly small number of units could be made economicallysince production of similar components for use in the buildingrepresents a substantial economic savings over previously proposedarrangements wherein different sized components are used at all parts ofthe building depending upon the loads applied.

Although illustrative embodiments of the present invention have beendescribed herein with reference to the accompanying drawings, it is tobe understood that the invention is not limited to those preciseembodiments and that various changes and modifications may be effectedtherein by one skilled in the art without departing from the scope orspirit of this invention.

What is claimed is:

l. A building structure including a plurality of flexible arches, aflexible membrane operatively connected to said arches in a foldedconfiguration having ridges and valleys therebetween with said flexiblearches being located at said ridges, and a plurality of prestressedflexible cables respectively located in the valleys formed in themembrane between two adjacent arches to hold said membrane in tensionagainst said arches, whereby said arches are braced against buckling bysaid membrane to form a relatively rigid structure; said arches beingformed of normally flat flexible members arranged to extend radiallywith respect to each other, to define a generally circular domestructure; and said structure including means for maintaining saidflexible members in an arched configuration; said prestressed cablesholding said membrane against said flexible arches upon downward flexingof said arches and said flexible arches holding said membrane againstsaid prestressed cables during upward movement of said arches wherebysaid membrane is held in tension against said arches under substantiallyall load conditions to brace said arches against buckling.

2. The building structure as defined in claim 1 wherein the innermostportions of said arches are located at a common point thereby to definesaid generally circular dome structure.

3. The building structure as defined in claim 2 wherein said means formaintaining said flexible arch members in an arched configurationincludes a peripheral cable operatively interconnecting the free ends ofthe arches.

4. The building structure as defined in claim 3 wherein each of saidarches is formed from two normally flat flexible elongated structuralmembers and said structure includes a central connecting ring for saidstructural members, said ring being operatively connected to one end ofeach at said structural members, with the structural members of eachpair extending in radial alignment from the ring.

5. The building structure as defined in claim 4 in which there are atleast four pairs of said structural members whereby said dome has anoctagonal shape in plan.

6. The building structure as defined in claim 4 including a plurality ofinverted V-shaped dome support members associated respectively with thefree ends of said arches, said support members being operativelyconnected to said arches at the apices thereof.

7. The building structure as defined in claim 6 wherein said membraneextends beyond the free ends of said arches to span between said supportmembers.

8. The building structure as defined in claim 7 wherein said radiallyextending cables are secured at one end to said central connecting ringand at their opposite ends to said support members.

9. The building structure .as defined in claim 8 wherein said supportmembers form a side wall of said building and provide access theretothrough the inverted V-shaped opening formed thereby.

10. The building structure. as defined in claim 8 wherein said oppositeends of said cables are operatively secured to the free'ends of theadjacent legs of two of adjacent inverted V-shaped support members.

11. The building structure as defined in claim 7 including cable meansoperatively connected between the edge of said membrane and the legs ofeach of said inverted V-shaped support members for transferring stressin the membrane to the support members.

12. The building structure as defined in claim 11 wherein said cablemeans are secured to said support members only at the apex and ends ofthe legs thereof whereby the stress transferred to said support membersstress said support members in compression only.

1. A building structure including a plurality of flexible arches, aflexible membrane operatively connected to said arches in a foldedconfiguration having ridges and valleys therebetween with said flexiblearches being located at said ridges, and a plurality of prestressedflexible cables respectively located in the valleys formed in themembrane between two adjacent arches to hold said membrane in tensionagainst said arches, whereby said arches are braced against buckling bysaid membrane to form a relatively rigid structure; said arches beingformed of normally flat flexible members arranged to extend radiallywith respect to each other, to define a generally circular domestructure; and said structure including means for maintaining saidflexible members in an arched configuration; said prestressed cablesholding said membrane against said flexible arches upon downward flexingof said arches and said flexible arches holding said membrane againstsaid prestressed cables during upward movement of said arches wherebysaid membrane is held in tension against said arches under substantiallyall load conditions to brace said arches against buckling.
 1. A buildingstructure including a plurality of flexible arches, a flexible membraneoperatively connected to said arches in a folded configuration havingridges and valleys therebetween with said flexible arches being locatedat said ridges, and a plurality of prestressed flexible cablesrespectively located in the valleys formed in the membrane between twoadjacent arches to hold said membrane in tension against said arches,whereby said arches are braced against buckling by said membrane to forma relatively rigid structure; said arches being formed of normally flatflexible members arranged to extend radially with respect to each other,to define a generally circular dome structure; and said structureincluding means for maintaining said flexible members in an archedconfiguration; said prestressed cables holding said membrane againstsaid flexible arches upon downward flexing of said arches and saidflexible arches holding said membrane against said prestressed cablesduring upward movement of said arches whereby said membrane is held intension against said arches under substantially all load conditions tobrace said arches against buckling.
 2. The building structure as definedin claim 1 wherein the innermost portions of said arches are located ata common point thereby to define said generally circular dome structure.3. The building structure as defined in claim 2 wherein said means formaintaining said flexible arch members in an arched configurationincludes a peripheral cable operatively interconnecting the free ends ofthe arches.
 4. The building structure as defined in claim 3 wherein eachof said arches is formed from two normally flat flexible elongatedstructural members and said structure includes a central connecting ringfor said structural members, said ring being operatively connected toone end of each at said structural members, with the structural membersof each pair extending in radial alignment from the ring.
 5. Thebuilding structure as defined in claim 4 in which there are at leastfour pairs of said structural members whereby said dome has an octagonalshape in plan.
 6. The building structure as defined in claim 4 includinga plurality of inverted V-shaped dome support members associatedrespectively with the free ends of said arches, said support membersbeing operatively connected to said archeS at the apices thereof.
 7. Thebuilding structure as defined in claim 6 wherein said membrane extendsbeyond the free ends of said arches to span between said supportmembers.
 8. The building structure as defined in claim 7 wherein saidradially extending cables are secured at one end to said centralconnecting ring and at their opposite ends to said support members. 9.The building structure as defined in claim 8 wherein said supportmembers form a side wall of said building and provide access theretothrough the inverted V-shaped opening formed thereby.
 10. The buildingstructure as defined in claim 8 wherein said opposite ends of saidcables are operatively secured to the free ends of the adjacent legs oftwo of adjacent inverted V-shaped support members.
 11. The buildingstructure as defined in claim 7 including cable means operativelyconnected between the edge of said membrane and the legs of each of saidinverted V-shaped support members for transferring stress in themembrane to the support members.